Electron-discharge device



Inventor 1 Henry J. Nolte Oct. 16, 1928.

b His Attovheg.

Patented Oct. 16, 1928.

UNITED STATES PATENT oFFlcE.

HENRY J'. NOLTE, OF SCHENECTADY, NEW YORK, .ASSIGNOR TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

ELECTRON-DISCHARGE DEVICE.

Application led February 7, 1921.

My prsent invention relates to electron discharge devices, and more particularly to devices ofthe type employing at least three electrodes, comprising ay cathode, an anode and a grid member for controlling the passage of an electron stream between cathode and anode. The object of my invention is to provide a simple and efficient construction for such devices which will be particularly adapted for controlling large amounts of power. In carrying my invention into effect I provide an evacuated receptacle which is composed in part of glass or vitreous material through which leading-in wires may be readily sealed, and in part of metal, the metal part, of the receptacle being adapted to serve as anode for the device.

u The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims; the invention itself, however, will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a view partly in section of one of my improved devices; Fig. 2 is a detail view of the seal for the leading-in conductors for supplying current to the cathode; Fig. 3 is a view of the grid and the structure whereby it is supported: Figs. 4 and 5 are detailviews of portions of the grid structure, and Fig. 6 is a sectional view of a modified construction which may be employed to advantage for supporting the grid within the receptacle.

As indicated in the drawing, I provide an evacuated receptacle comprising a. portion 1 of glass and a portion 2 of metal. The glass portion is sealed to the metal portion by means of a thin metal ring 3 which is preterably of copper or an alloy having substantially the same coefficient of expansion as the glass of which the part 1 is composed. This ring 8 is soldered or welded to the portion 2 and forms a gas tight seal with the glass at the region 4 where it is surrounded by the glass wall of the portion 1. The cathode 5. which is preferably of tungsten, is supported within the receptacle by means of supporting arms 6, 7 and 8, the arms 6 and 7 also serving as supply conductors to the cathode. In view of the fact that a large heating current must be supplied to the cathode in order to obtain a large electron emission and large output from the device, the leading-in conductors 9 and 10 are subdivided into a plurality of Serial No. 443,005.

parallel wires of smaller diameter at the region 11 where they are sealed through the wall of the reentrant tubular portion 12 of the glass member 1 in order that a gas tight seal may be made more readily than it can be made with a single large conductor. The parallel portion of these leading-in wires are secured to the supporting arms 6 and 7 by means of binding wires 13, and are also spot welded to the supporting arms at the points 14, as indicated. The grid l5 which surrounds the cathode is in the form of a cylindrical screen made up of two sets of wires 16, 17, which are wound spirally in opposite directions and interwoven. By means of this construction the principal expansion of the grid when heated will occur in the direction of its diameter and the tendency of the grid to buckle and make contact with the filament or anode will be largely eliminated. The ends of these two sets of grid wires are secured to end rings 18 and 19 by means of binding wires wound around these rings. Supporting arms 20 are secured t0 these two rings and together with the rings form a rigid support for the grid. These supporting arms and the end rings preferably are made of tungsten or similar metal from which the occluded gas may easily be removed so there is no tendency for the evolution of gas when the parts are heated during the normal operation of the device.

I have indicated in the drawing one convenient way of uniting the arms 20 with the rings 18 and 19. These rings are formed of a strip of metal 21 stamped out, as indicated in Fig. 5, with ears 22 projecting from its edges. This strip of metal is bent into the form of a ring, these ears bent over and the arms 20 inserted through the holes 23 in the ears 22. The arm 20, which passes through the holes 28 at the ends of the strip which come opposite each other, also serves to hold the two ends of the strip together. After the arms 20 are inserted in these holes theears may be squeezed or bent in such a way as to firmly grip the arms 20 and thereby secure the parts together without the necessity of any welded or soldered joints. The grid structure described is supported in the desired position in the receptacle by means of a sleeve 211 which surrounds the reentrant tubular portion 12 and is securely fastened thereto by means of clamping screw 25. Supporting arms 26 are secured to this sleeve 24 and the members 20 which are of considerably smaller diameter than the diameter of the arms 26 are fastened to the arms 26 in the manner indicated at 27 in Fig. 3. For convenience in the construction of the device the end ofthe portion 2 of the receptacle may be left open until the parts have been sealed together and then closed by means olla cap 28 which is soldered to the receptacle or welded thereto to form an air tight joint.

In the operation of he device described for the control of large energies, the anode 2 should be artificially cooled. This may be accomplished by placing it in a bath of water or other suitable cooling liquid and providing means to insure good circulation of the cooling liquid. In view of the fact, therefore, that the anode 2 will normally operate at a low temperature, it is possible to make use of metal for its construction having a comparatively low melting point. I have found that copper is very suitable for this purpose.

In the exhaustion of the device described, to remove all air as well as all the gases occluded in the metal parts, I prefer as a preliminary step to heat the anode 2 by means of heat radiated from the cathode 5. It is possible to heat the anode to red heat in this way and thereby drive oi a large portion of the occluded gases. After the exhaustion has been carried on in this way until the evolul tion of gas is greatly decreased or substantially stopped, a source of potential is connected between cathode and anode so that the anode will be bombarded by electrons emitted from the cathode. At this point in the eX- haust the cooling medium is applied to the anode and the gas removed during this stage is therefore removed principally as a result of bombardment. Occluded gas is also removed from the grid structure by bombarding the grid and its supporting parts by electrons given 0E from the cathode.

In the construction indicated in Fig. 1 it will be noted that the sleeve 24 which supports the grid is separated from the leadingin conductors 9 and 10 only by the glass wall of the tubular portion 12 and the air space between this glass wall and the leading-in conductors. In cases where the device is operated at high potentials the potential diiierence between the grid and cathode may become so large as to break down this insulation between the sleeve 24 and the leading-in conductors. To avoid such a contingency the construction shown in Fig. 6 may be used. In this case the tubular portion l2 is surrounded by cylindrical member 29 intergrally united thereto at one end and the sleeve 24 isclamped to this cylindrical member 29. In this case there will be an evacuated space 30 between the sleeve 24 and the leading-in conductors 9 and l0 and as a result a much higher degree of insulation will be obtained between the grid and the leading-in conductors.

While I have indicated and described the preferred embodiments of my invention, it will be understood that my invention is by no means limited to the particular structures shown as many modifications in the arrangement of parts and their relation to one another may be made without departing from the scope of my'invention as set forth in the appended claims.

l/Vhat I claim as new and desire to secure by Letters Patent of the United States, is

1. A grid structure for an electron discharge device comprising a plurality of wires interwoven to form a screen all of said Wires extending in directions at an acute angle to the longitudinal axis of the grid.

2. A grid structure of substantially cylindrical form for an electron discharge device comprising two sets of wires spirally wound in opposite directions, the two sets of wires being interwoven to form a screen.

3. A grid structure of substantially cylindrical form for an electron discharge device comprising a plurality of wires interwoven to form a screen, the wires being so arranged that the principal expansion of the screen when heated will be in the direction' of its diameter.

4. A grid structure of substantially cylindrical form for an electron discharge device comprising two sets of wires spirally wound in opposite directions, the two sets of wires being interwoven to form a screen, and a ring at each end of said screen to which the ends of said sets of wires are secured.

5. A grid structure of substantially cylindrical form for an electron discharge device comprising two sets of wires spirally wound in opposite directions, the two sets of wires being interwoven to form a screen, a ring at each end of said screen to which the ends of said sets of wires are secured, and rigid supporting members connecting said rings.

6. A grid structure of substantially cylindrical form for an electron discharge device comprising two sets of wires spirally wound in opposite directions, the two sets of wires being interwoven to form a screen, a ring at each end of said screen to which the ends of said sets of wires are secured, and rigid supporting members inside of said screen connecting said rings.

7 The combination in an electron discharge device of an electron emitting cathode and a discharge controlling grid, enclosed in an evacuated receptacle, a reentrant tubular member of vitreous material through which. the leading-in conductors for said cathode are sealed and a supporting member for the grid surrounding said reentrant tubular member and supported thereby, said grid supporting member being separated from said tubular member by an evacuated space.

8. The combination in an electron discharge device of an electron emitting catho le and a discharge controlling grid enclosed in an evacuated receptacle, a reentrant tubular member of vitreous material through which the leading-in conductors for said cathode are sealed, a cylindrical member of vitreous material surrounding said tubular member and separated therefrom by a vacuous space and a supporting member for said grid surrounding said cylindrical member and in engagement therewith.

9. The combination in an electron discharge device of an electron emitting cathode and a discharge controlling grid enclosed in an evacuated receptacle, a reentrant tubular member of vitreous material through which the leading-in conductors for said cathode are sealed, a cylindrical member of vitreous material surrounding said tubular member supported thereby at one end and separated therefrom by a vacuous space, and a supporting member for said grid surrounding said cylindrical ymember and in engagement therewith.

10. An electron discharge device comprising an evacuated receptacle, an electron emitting cathode and a 'second electrode mounted therein, leading-in conductors for saidcathode, and a vitreous support for said second electrode, said support surrounding said leading-in conductors and being spaced from said leading-in wires by an evacuated space.

11. An electron discharge device comprising an evacuated receptacle, an electron emitting electrode and a second electrode mounted therein, leading-in conductors for said electron emitting electrode, a cylindrical member of vitreous material connected to said receptacle, said member lsurrounding the leading-in conductors and being spaced from said leading-in conductors by an evacuated space, and a supporting member for said second electrode surrounding said cylindrical member and in engagement therewith.

12. An electron discharge device comprising an evacuated receptacle having a vitreous portion and a metallic portion, the metallic portion comprising an anode, an electron emitting cathode, and a grid mounted in said receptacle, leading-in wires for said cathode, a cylindrical member of vitreous material mounted on said receptacle and surrounding said leading-in conductors, said member being spaced from said leading-in wires by an evacuated space, and a supporting member for the grid mounted onk said cylindrical member.

In Witness whereof I have hereunto set my hand this 4th day of February, 1921.

' HENRY J N OLTE. 

